Dogwood tree named ‘Jean&#39;s Appalachian Snow’

ABSTRACT

A new and distinct cultivar of Dogwood tree,  Cornus florida , named ‘Jean&#39;s Appalachian Snow’, is provided. This cultivar is characterized by resistance to powdery mildew which is superior to any other white flowering dogwood.

CROSS-REFERENCE TO A RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/210,603, filed Jun. 9, 2000.

BACKGROUND OF THE INVENTION

The present invention relates to a new and distinct cultivar offlowering dogwood which is resistant to powdery mildew. This dogwood isbotanically known as Cornus florida and hereinafter is referred to bythe cultivar name ‘Jean's Appalachian Snow’.

This new dogwood cultivar was discovered in a field planting ofapproximately 1,100,000 Cornus florida seeds in Decherd, Tenn. in 1994.‘Jean's Appalachian Snow’ is a white flowering dogwood which, to theknowledge of the inventors, is superior to any other white floweringdogwood cultivar with respect to powdery mildew resistance. Asexualreproduction of ‘Jean's Appalachian Snow’ by terminal cuttings rooted atthe Tennessee Agricultural Experiment Station in Knoxville, Tenn. hasshown that the unique features of this new dogwood cultivar are stableand reproduced true to type in successive vegetative generations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. Photograph of a typical flower specimen of ‘Jean's AppalachianSnow’. This photograph is a closeup view of a typical flower of thiscultivar.

FIG. 2. A similarity index for various dogwoods.

FIG. 3. Cluster analysis of various dogwoods.

FIG. 4. Principal coordinate analysis of the relationships between thedogwoods.

Flower colors in the photographs may differ from the actual colors dueto light reflectance.

DETAILED DESCRIPTION OF THE NEW VARIETY

The parental lineage of this cultivar is unknown. ‘Jean's AppalachianSnow’ is a white flowering dogwood cultivar isolated from a fieldplanting of approximately 1,100,000 Cornus florida seeds in Decherd,Tenn. Seeds were bulked from collections of wild and landcape trees fromTennesee, North Carolina, Alabama, and Georgia. This cultivar may bereproduced asexually by rooting cuttings and by grafting.

‘Jean's Appalachian Snow’ has white bracts which are overlapping. Thebracts are similar in size to the bracts of ‘Cherokee Princess’. Upperpairs of bracts average about 15.8 cm long by about 11.2 cm wide in size(n=30). Clefts at the ends of the bracts are indented and have littlepigmentation. Flower petals are yellow and flowers average 23 perinflorescence (n=15).

‘Jean's Appalachian Snow’ is, to the knowledge of the inventors,superior in resistance to powdery mildew to any other white floweringdogwood cultivar. This cultivar has been tested for four (4) years. Testplants were exposed to powdery mildew and assessed for resistance topowdery mildew. Mildew scores for ‘Jean's Appalachian Snow’, controlplants, and ‘Cherokee Brave’ were obtained using the following scale:0=healthy; 1=≦2% of foliage with signs or symptoms of powdery mildew;2=≦10% of foliage with signs or symptoms of powdery mildew; 3=≦25% offoliage with signs or symptoms of powdery mildew; 4=≦50% of foliage withsigns or symptoms of powdery mildew; 5=≦75% of foliage with signs orsymptoms of powdery mildew; 6=≦100% of foliage with signs or symptoms ofpowdery mildew. Table 1 presents the data obtained over the last fouryears.

Year ‘Jean's Appalachian Snow' Control Score¹ ‘Cherokee Brave'² 1995 0.05.0 (a) — 1996 0.0 5.0 (b) 1.2 1997 0.0 4.6 (b) 2.3 1998 0.0 4.8 (c) 2.1¹Control plants were (a) Cornus florida seedlings, (b) ‘CherokeeSunset', or (c) ‘Cherokee Daybreak' that were of similar age and size.²‘Cherokee Brave' is a pink flowering dogwood cultivar which is the onlycultivar known to the inventors to possess partial resistance to powderymildew.

DNA amplification fingerprinting was used to type ‘Jean's AppalachianSnow’, ‘Kay's Appalachian Mist’, and ‘Karen's Appalachian Blush’. Themethodology followed that of Trigiano and Caetano-Anollés(HortTechnology, 8:413-423 [1998]). Data, obtained from 235 locigenerated from genomic DNA using seven (7) arbitrary octomeric primers,was used to compare the powdery mildew resistant dogwoods of the subjectapplication to other dogwoods (including powdery mildew resistant linesand cultivars commonly found in nurseries). The sequences of the primerswere as follows: 1) GAGCCTGT, 2) GTTACGCC, 3) CTGTGAG, 4) GTAACGCC, 5)GACGTAGG, 6) GATCGCAG, and 7) GTATCGCC. DNA amplification fingerprintinganalysis as well as the cluster and principal coordinate analysis werecompleted using the NTSYS PROGRAM, pc version 2.2 (Exeter Software, 100N. Country Road, Sedtauket, N.Y. 11733). A similarity index is providedin FIG. 2. FIG. 3 depicts the resulting cluster analysis. FIG. 4 depictsthe principal coordinate analysis of the relationships between thedogwoods.

The abbreviations found in the Figures are as follows: AS=‘AppalachianSpring’, KAM=‘Kay's Appalachian Mist’, JAS=‘Jean's Appalachian Snow’,C9=‘Cloud Nine’, KAB=‘Karen's Appalachian Blush’, CP=‘CherokeePrincess’, SPR=‘Springtime’ and CB=‘Cherokee Brave’. All are white bractdogwoods except CB, which is red.

DETAILED BOTANICAL DESCRIPTION

The following observations, measurements, and comparisons describe thecultivar grown in Knoxville, Tenn. under container nursery conditionswhich approximate commercial production conditions. Dogwoods used forthis description were about six (6) years old and were grown intwenty-five (25) gallon containers. Plant hardiness is expected to bezones 5-9.

The following description uses color references to The RoyalHorticultural Society Colour Chart, except where general terms ofordinary dictionary significance are used. All color ratings were onadaxial surfaces. Color ratings for abaxial surfaces were not obtainedbecause reflected/refracted light, due to the density of pubescence onabaxial surfaces, made accurate color determinations difficult orimpossible. Measurements are provided as a range with the middle valueproviding the average (lower limit<average value<upper limit).

Botanical classification: Cornus florida, cultivar Jean's AppalachianSnow.

Parentage: Unknown.

Propagation:

Type.—Terminal softwood cuttings.

Time to initiate roots (in June).—About 3-4 weeks at about 25-30° C.

Rooting hormone.—5,000-10,000 ppm; Five (5) second quick dip in DIP ‘N’GROW (1% IBA, 0.5% NAA), (Dip ‘N’ Grow, Inc., Clackamas, Oreg.).

Intermittent mist.—Six (6) seconds every six (6) minutes; light: 30-50%shade over propagation bench.

Media.—Peat-perlite.

Rooting habit.—Profuse from base of cutting.

Plant description:

Plant form and growth habit.—Perennial deciduous tree, mostly uprightwith horizontal branching.

Plant size.—A six (6) year old tree will attain a height of about 200 cmand a width of about 130 cm.

Vigor.—Similar to other Cornus florida cultivars.

Branching habit.—Moderate, branch crotch angles of about 30-45° to maintrunk.

Main stem/trunk description.—Diameter: About 3.1 cm; bark texture:smooth; bark color: gray 201C.

Lateral branch description.—Branch angle of about 50° with a range of47°-55°.

Foliage description:

Arrangement.—Simple, opposite; leaves mostly crowded towards branchapices.

Leaf blade length (cm).—About 12.8<13.8<15.5 (n=5).

Leaf blade width (cm).—About 7.0<8.4<9.0 cm (n=5).

Petiole length (cm).—About 1.1<1.24<1.5 (n=5).

Petiole diameter (mm).—About 1.23<1.29<1.37 (n=5).

Shape.—Broadly ovate.

Apex.—Acuminate, leaf tip with 90° twist.

Base.—Mostly acute, about 10% are unequal.

Margin.—Entire, slightly undulate.

Leaf vein pairs.—5.5-6, opposite to alternate. Petiole reflexed 80-90%from plane of leaf blade.

Bipolar trichomes.—Upper surface (μ) — sparse; 6<6.9<12. Lower surface(μ) — dense; 8<11.9<16.

Texture.—Upper surface: Nearly glabrous. Lower surface: Leaf hairs — onveins, and vein axils (μ), 16<22.1<38.

Color.—Yellow green 144B.

Flower description:

Fragrance.—None observed.

Flower bud size.—Width: 8.2 mm (widest diameter). Length: 6.5 mm (baseto tip).

Shape of involucral bracts.—Obovate.

Apex shape of involucral bracts.—Emarginate.

Base shape of involucral bracts.—Cuneate.

Number of bracts.—4 (in two pairs).

Natural flowering season.—1999: about 15 days (April 12 through April27). 2000: about 19 days (April 6 though April 25). 2001: about 14 days(April 14 through April 27).

Inflorescence arrangement.—Typical for species, large bracts overlap.

Inflorescence diameter.—About 32 cm wide.

Bract dimensions.—Upper bracts 15.8 cm long by about 11.2 cm wide(n=30). Inflorescence is 6.8 mm wide; anther length is 1.4 mm. Floraldevelopment is asynchronous among inflorescence.

Color (abaxial and adaxial surfaces).—White bracts (155D); bract cleftshave, either no pigmentation or little pigmentation of yellow green(150B) color.

Sepals.—Typically 4.

Stamens.—Typically 4.

Pistil.—Typically 1.

Petal color (abaxial and adaxial surfaces).—Yellow green 151B.

Flower number.—22.

Ovary.—Bilocular with each locule having 1 ovule.

Fruit description:

Berry type.—Drupe (about 14 mm by 7 mm) aggregated in one mass.

Color.—5R({fraction (5/10)}) using Munsell Color Chart for Plant Tissues(Munsell Color, Baltimore, Md. 21218).

Seed.—Typical for species.

Disease resistance: this cultivar demonstrated outstanding resistance topowdery mildew superior to that of any other white flowering dogwoodcultivar known to the inventors. No susceptibility to other diseases orarthropod pests was observed.

What is claimed is:
 1. A new and distinct cultivar of Dogwood tree,Cornus florida, named ‘Jean's Appalachian Snow’, as illustrated anddescribed.